In small cross-section hard rock roadway blasting for metal mines,common challenges include low energy utilization of explosives,short excavation footage per cycle,and large blocks of rock fragmentation.Taking the -780 m four-level main roadway at Canzhuang Gold Mine as a case study,a simulation analysis was conducted using blasting damage,stress,and velocity change as evaluation indicators for 4 charging structures:no stemming,stemming＋air gap charging,stemming＋water medium gap at the collar,and stemming＋water medium gaps at both ends.The optimal charge structure parameters were selected for field tests.The results showed that adding stemming effectively prevented energy loss and improved energy utilization.Adding water bags at the collar extended the stemming time,maintained higher detonation pressure,and prolonged the effective action,resulting in more efficient rock fragmentation.Replacing part of the explosive with water bags at the bottom of the hole maintained the blasting effect while preventing overbreak.Overall,the stemming＋water medium gap charging structure at both ends was found to be the most effective.Field tests demonstrated that the optimized charge structure increased the borehole utilization rate to an average of 95 %,15 % higher than that before optimization.